The application discloses a biaxial cruciform tensile testing device, which comprises a cruciform pedestal. The cruciform pedestal is provided with a cruciform groove. Each trapezoid block base slides along each corresponding sectional groove. A baffle plate is arranged on each trapezoid block base. Each trapezoid block is arranged at one side of the baffle plate towards the central position of the cruciform pedestal. A clamping part is fixedly arranged at one end of each trapezoid block base. A tension sensor is arranged between the trapezoid block base and the clamping part. A press-down head is arranged at the central position of cruciform press-down arms. The bottom edge of each trapezoid block leans against the corresponding baffle plate, and the beveled edge of the trapezoid block is abutted against a roller at the top of the corresponding cruciform press-down arm. The cruciform press-down arm is provided with a right-angle location hole, through which a locating pin passes; and the bottom and the right angle at the center of the cruciform groove are fixed together. A spring sleeves the locating pin. The inner wall of the cruciform pedestal is provided with grooves, in which scale gratings are arranged. A grating reading head corresponding to each scale grating is arranged on the trapezoid block base. According to the device provided by the embodiment, by stretching a test piece at uniform speed in the horizontal direction, accuracy of testing tensile property of the material is raised.